In addition to Phage0070's comment, it is important to note that the volume at a pump is corrected to a certain temperature and pressure, through simple ratios. This means that the "below threshold" comments are indeed completely false, as the average fuel tank is not able to make this correction. In other words, while a car would interpret hot fuel as occupying a larger volume, and cold fuel as occupying less, a pump would correct these volumes to a standard, and display an appropriate price.